<!DOCTYPE html>
<!-- Any copyright is dedicated to the Public Domain.
   - http://creativecommons.org/publicdomain/zero/1.0/ -->

<html>
  <style>
  div#details {
    background-color: orange;
    overflow: auto;
    width: 300px;
    height: 200px;
  }
  div#summary {
    background-color: green;
    overflow: auto;
    width: 200px;
    height: 100px;
  }
  div.tall {
    background-color: blue;
    border: 1px dotted purple;
    height: 1000px;
    width: 50px;
  }
  </style>
  <body>
    <div id="details">
      <div id="summary">
        <div class="tall">
        </div>
      </div>
      <div class="tall">
      </div>
    </div>
  </body>
</html>
